1. Field of the Invention
The present invention pertains to patient interface devices structured to deliver a flow of breathing gas to a user, and, in particular, to a sealing cushion for a patient interface device that has an angled sealing flap providing an improved fit and seal.
2. Description of the Related Art
There are numerous situations where it is necessary or desirable to deliver a flow of breathing gas non-invasively to the airway of a patient, i.e., without intubating the patient or surgically inserting a tracheal tube into the patient's esophagus. For example, it is known to ventilate a patient using a technique known as non-invasive ventilation. It is also known to deliver positive airway pressure (PAP) therapy to treat certain medical disorders, the most notable of which is OSA. Known PAP therapies include continuous positive airway pressure (CPAP), wherein a constant positive pressure is provided to the airway of the patient in order to splint open the patient's airway, and variable airway pressure, wherein the pressure provided to the airway of the patient is varied with the patient's respiratory cycle. Such therapies are typically provided to the patient at night while the patient is sleeping.
Non-invasive ventilation and pressure support therapies as just described involve the placement of a patient interface device including a mask component having a soft, flexible sealing cushion on the face of a patient. The mask component may be, without limitation, a nasal mask that covers the patient's nose, a nasal/oral mask that covers the patient's nose and mouth, or a full face mask that covers the patient's face. Such patient interface devices may also employ other patient contacting components, such as forehead supports, cheek pads and chin pads. The sealing cushion typically has a support portion coupled to a sealing flap portion, which may integrated together as a single part or that may be separate components that when combined together in the final assembly provide the sealing and support functions. The patient interface device is connected to a gas delivery tube or conduit and interfaces the ventilator or pressure support device with the airway of the patient, so that a flow of breathing gas can be delivered from the pressure/flow generating device to the airway of the patient. It is known to maintain such devices on the face of a wearer by a headgear having one or more straps adapted to fit over/around the patient's head.
Patient interface devices used in non-invasive ventilation and pressure support therapies should be comfortable and maintain a robust seal, while at the same time optimizing comfort by avoiding the creation of excessive pressure and/or red marks on the user's face. The sealing flap portion should also conform to the face without excessive bunching and encroaching on the patient's eyes, cheeks, and nostrils. As used herein, the term “bunching” shall refer to an area where, when the sealing cushion is donned by the user, extra sealing flap length collects and folds/curls over itself, resulting in bunches or folds of sealing flap. Bunching can cause patient annoyance, obstruct the patient's view, partially obstruct the patient's air path, and/or create potential leak paths, any or all of which may ultimately decrease the patient's therapy compliance.
Unfortunately, many current patient interface devices used in non-invasive ventilation and pressure support therapies have sealing problems, create pressure on the face, and/or cause red marks and/or sores. One location where such problems, especially pressure points, frequently occur is on and around the portion of the patient's mouth above the upper lip. The occurrence of these problems may often be attributed to the amount of sealing surface area created by traditional sealing flap geometries. Patients also often complain about traditional sealing flaps partially blocking their nostrils and reducing the ease of their breathing.
The problems described above are primarily due to the geometry utilized in current sealing cushions. More specifically, traditional sealing flap/cushion designs consist of a seal interface in which the aperture primarily exists in a single plane from nose-bridge to upper lip area. In such designs, there is a small distance (0 to 10 mm) between the horizontal plane that intersects the nose bridge and the horizontal plane that intersects at the upper-lip area. This forces the sealing flap to contact the nose, cheeks, and upper lip at nearly the same time when donned by a patient. As a result, forces are applied to all these areas from the time of initial contact between the face and the mask. As force is applied to achieve a seal at the nose, cheeks, and upper lip, all of these areas will experience increasing compression from the time of initial contact until the time a seal is made. This causes undesired excessive force on those areas of an individuals' face which protrude out the furthest.
In addition, traditional sealing flap/cushion designs employ a large sealing surface area across and down onto the lip towards the mouth. This is again primarily due to the opening geometry of traditional sealing flap/cushion designs. In particular, the aperture's single plane opening results in a seal length at the upper lip area that is large. This is done to ensure sufficient sealing area across the nose bridge, while at the same time across and down the upper lip. As noted above, these traditional geometries require the nose and upper lip to contact the sealing interface at the same time, putting significant pressure on both areas of the face. Also, the sealing flap has to be far enough above any supporting cushion (integrated or not to the sealing flap) to ensure that there is a seal between the support geometry and the patient's upper lip. These constraints result in excessive flap length which consequently covers the majority of the patient's upper lip. This also often results in bunching of the sealing flap at the upper lip, which can reduce the quality of the seal and cause user discomfort and annoyance. Furthermore, the longer flap geometry of traditional designs as just described often results in the sealing flap riding up and partially occluding the airflow into the patient's nostrils (i.e., nostril encroachment), which typically makes breathing more difficult. Users may attempt to avoid this problem by wearing the masks further down on the upper lip. This, however, often results in additional contact area for lip pressure and discomfort to occur.